The present invention relates to a solid-state image sensor device in which a voltage signal is obtained from an incident light through photoelectric conversion and its driving method, in particular, it relates to a solid-state image sensor device and its driving method being able to correspond to both progressive mode and interlaced mode.
In recent years, a solid-state image sensor device being able to correspond to the read-out of signals in both progressive mode (hereinafter referred to as PS mode) and interlaced mode (hereinafter referred to as IS mode) are known to the public.
In the PS mode, the read-out of signals is performed by a system called the read-out over the whole picture elements. In other words, when the read-out of signals is performed in the PS mode, all picture element signals obtained by the scanning at one time are independently output without being mixed.
On the other hand, in the IS mode, scanning is performed by a system called an interlaced scanning, for example, 525 scanning lines are scanned alternately, and a first field (even field) and a second field (odd field) are obtained by respective scannings and they are superposed to obtain a frame of an image. In the read-out of signals in the IS mode, element signals being adjacent to each other in the vertical direction are output being mixed, and so called field-read forms a leading system in which at the first time, the first field is scanned, and at the next time, the second field is scanned to fill up the gaps between the first scanning lines.
In a conventional solid-state image sensor device as described in the above, in the IS mode the field-read is performed in which 2 element signals being adjacent to each other in the vertical direction are mixed and output, in contrast to this, in the PS mode, each picture element signal is independently output without being mixed. Therefore, in the PS mode, one signal for each picture element is output, so that a saturate signal quantity becomes a half in comparison with that in the IS mode.
The saturation signal quantity means a maximum signal quantity when a solid-state image sensor device outputs a right signal, in short, it is decided dependent on the quantity of charge which can be accumulated in a photodiode in a solid-state image sensor device corresponding to a picture element in an image. The dynamic range of a solid-state image sensor device is defined by the ratio of the saturation signal quantity to the noise level, therefore the decrease in the saturation signal quantity results in the degradation in the dynamic range.